Detent, which is also known as “cogging torque” or “detent torque,” is a periodic torque created in an electro-dynamic structure that co-axially integrates high permeability elements, such as field poles, into a stator structure, which, in turn, is formed with permanent magnets in a rotor structure. When either structure is rotated with respect to the other, a periodic varying torque can be created because the magnet structure prefers to align centered on the high permeability elements rather than at the intervening field pole gaps of air between the field pole elements. This detent torque can be created by the portion of the area of the magnet that is not immediately facing the field pole shoe. Each incremental area of the face of the magnet that is facing an gap between the field pole shoes is then attracted to the nearest surface of an adjacent field pole of high permeability, thus creating an incremental torque in that direction. The resulting detent torque can be viewed as the summation of the incremental torques over all the areas not facing a high permeability region in the entire interface region between the stator and rotor structure. The magnitude of this varying detent torque increases as the gap between field pole elements can increase because a greater portion of the magnet area is in the gap between field poles. While it is desirable to minimize detent torque, decreasing the field pole gap between field pole elements has limitations because flux leakage between field poles increases.
In view of the foregoing, it would be desirable to provide stator and rotor-stator structures that minimize the drawbacks of conventional motors and generators to reduce detent, among other things.